Factors Affecting Adsorption
Nature of adsorbent Same gas may be adsorbed to different extents on different adsorbent .
Surface area of the adsorbent Greater the surface area , greater is the extent of adsorption .
Nature of the gas being adsorbed Greater is the critical temperature of a gas , greater are the van der Waals ’ forces of attraction and thus , greater is the adsorption .
Temperature Adsorption is an exothermic process involving the equilibrium Gas ( adsorbate ) + Solid ( adsorbent ) ⇔ Gas adsorbed on solid + Heat
Applying Le-Chatelier principle , increase of temperature decreases the adsorption and vice-versa .
Pressure Adsorption increases with pressure at constant temperature . The effect is large if temperature is kept constant at low value .
Activation of the solid adsorbent Activation means increasing the adsorbing power of the solid adsorbent . This can be done by subdividing the solid adsorbent or by removing the gases already adsorbed by passing superheated steam .
Adsorption Isotherms
It is the plot of the mass of gas adsorbed per gram of adsorbent ( x / m ) versus equilibrium pressure at constant temperature .